1. Field of the Invention
The present invention relates to an occupant classification device that detects the seating state of an occupant and an airbag device that controls the operation of an airbag based on the seating state.
2. Description of the Related Art
There have been known devices that detect a distance between an object and a predetermined position, including various known methods that detect the distance. The detection result is used for various control parameters. For example, in an airbag system that inflates an airbag to protect a seat's occupant against an impact in a vehicle collision, a technique of detecting a distance between the occupant and a predetermined position for controlling the airbag operation has been proposed (see for example Japanese Patent Laid-Open (KOKAI) No. 2001-213268).
The airbag system detects an impact in the event of a vehicle collision and inflates the bag by a prescribed explosive force. If the distance between the airbag and the occupant is small because of the sitting posture of the occupant, the inflated airbag could possibly injure the occupant. Accordingly, the technique disclosed by Japanese Patent Laid-Open (KOKAI) No. 2001-213268 is directed to a solution to the problem where a distance between a predetermined position in front of the occupant and the occupant is measured, and the operation of the airbag is controlled based on the measured distance.
According to the disclosed technique, a spot beam light is directed toward the seat's occupant, and a distance to the occupant is detected based on the image of the occupant irradiated with the beam light, i.e., based on the position of the beam light in the image. In this way the distance to the position irradiated with the beam light can be detected, but the distance to the other body parts cannot be detected. Therefore, the accurate seating state of the occupant in the seat cannot be determined.
More specifically, since the object for distance detection can be in various postures, similar to a seat's occupant in a vehicle, a distance to a position of one part of the object can be specified, but the distance to another part of the object cannot be specified. By the distance detecting method, not only is the seating state of the seat occupant inaccurately detected but also the airbag cannot appropriately be controlled based on the seating state.